I've smoked jerky successfully at temps as cold as -15F. Two methods I've used to retain heat in the cook chamber, this was on two different electric smokers.
I had a very nice custom stainless steel smoker I acquired which a friend who is a carpenter built a wood box around it then wrapped the box in 2" foam board insulation. The other was a home built electric smoker I made from a small fridge. I simply wrapped that smoker with a thick old wool blanket ( wool holds up to 70% of its heat value even when wet ).
For each of these I poked a hole in the front of the smoker and pushed a probe style thermometer through the insulation and into the cook chamber to monitor the chamber temp. If you have a wireless therm you wouldn't need to do that.
I'm sure you'll get other ideas from the members here, just relaying what worked for myself. Hope this helps. - Ed